CARACAS, Venezuela (AP) — Venezuela’s government imposed rolling blackouts of four hours every other day throughout the country on Tuesday to combat an energy crisis.

President Hugo Chavez has said rationing is necessary to prevent water levels in Guri Dam — the cornerstone of Venezuela’s energy system — from falling to critical lows and causing a widespread power collapse. Drought has cut the flow of water into the dam, which feeds three hydroelectric plants that supply 73 percent of Venezuela’s electricity.

“This plan is going to be implemented troughout the country,” Electricity Minister Angel Rodriguez said. “In some places, it will be four hours, in others it will be two or three hours.”

Rolling blackouts will begin in the capital of Caracas on Wednesday, said Javier Alvarado, president of the city’s state electric utility.

Government officials had already imposed some cuts to help the country get through the dry season until May, when seasonal rains are predicted to return.

The government recently reduced the hours of electricity supply for shopping centers and required businesses and large residential complexes to cut energy use by 20 percent or face fines.

Chavez’s government has also partially shut down state-run steel and aluminum plants. The president announced last week that many public employees will have shorter workdays — from 8 a.m. to 1 p.m. — except those in offices that tend to the public.

“With these measures, we’re trying to keep Guri from taking us to a very critical situation at the end of February, from creating let’s say a total shutdown of the country,” Rodriguez told state television Monday night as he announced the nationwide rationing plan.

Some parts of the country have already been enduring unplanned blackouts for months, as demand has outstripped the electrical supply. The energy output from the Guri Dam’s three hydroelectric plants has also declined below its normal capacity.

The increased rationing will help cover a 12 percent gap between energy supply and demand, due to the situation at Guri and at some thermoelectric plants that are operating below capacity, Alvarado said.

He said water levels at the dam in southeastern Venezuela have dropped drastically as a result of the El Nino weather phenomenon in the Pacific Ocean, saying “it’s a global phenomenon and it’s affected us in recent months.” He noted there has been particularly little rain in southeastern Venezuela, where the watershed that feeds Guri is located.

Chavez’s critics say his government is to blame because it has failed to complete enough power upgrades to keep up with increasing demand despite Venezuela’s bountiful oil earnings.

Alvarado said the Caracas subway, hospitals, media outlets and public institutions that tend to the public would not be affected.